Abstract: The present study used spatial autocorrelation analysis, geo-detector and mixed geographically weighted regression (MGWR) methods to analyze the 2017-2019 PM_2.5 data of three urban agglomerations along the Yangtze River Economic Belt under the National Monitoring System and established multiple spatial scales, multiple impact indicators and multiple analysis models for a comprehensive assessment of the PM_2.5 concentrations. The results showed that: (1) The PM_2.5 concentration in the three urban agglomerations had a generally downward trend over the three years. The average PM_2.5 concentration in the Yangtze River Delta urban agglomeration was the lowest for the three years under the study, and the average PM_2.5 concentration in the Yangtze River Middle-Reach urban agglomeration was the highest for the three years, but the decline was the largest. The air quality in the Cheng-Yu urban agglomeration was overall between the levels of the two aforementioned agglomerations. (2) On the seasonal scale, PM_2.5 concentration was higher in the spring and winter, but lower in summer and autumn. (3) From the spatial perspective, air pollution in the north of the Yangtze River was more severe than that in the south of the Yangtze River. The air quality in the eastern and southern parts of the Yangtze River Delta urban agglomeration was better than that in other regions of the same agglomeration. The air quality in the northwest part was worse than other regions of the Yangtze River Middle-Reach urban agglomeration, and for the Cheng-Yu urban agglomeration, the air quality in the eastern part was better. (4) Meteorological elements and socio-economic status were the main factors affecting the PM_2.5 concentration. Among social and economic factors, the urbanization rate was found to be most impactful for PM_2.5 pollution from 2017 to 2019, followed by industrial enterprises above designated size. Among meteorological factors, total precipitation, maximum temperature and other factors showed a strong weakening effect on PM_2.5 pollution. In general, the current urbanization process had a greater impact on PM_2.5 pollution.